-------------------------wxml  
<view class="t2">
    <view class="t3">地点：</view>
    <view class="t4">
    <picker mode="selector" bindchange="bindPickerChange4" value="{{didianArr[di_index].id}}" range="{{didianArr}}" range-key="{{'diname'}}">
      当前选择：{{didianArr[di_index].diname}}
    </picker>
    </view>
  </view>
-----------------------js
var app = getApp();
const db = wx.cloud.database();
Page({
data: {
    didianArr:[],
    onLoad(options) {
    var that = this
    //获取数据库中didian数据
    db.collection('didian')
    .get({
      success(res) {
        // res.data 是包含以上定义的两条记录的数组
        console.log('请求成功',res.data)
        that.setData({
          didianArr:res.data
        })
      }
    })

  },

  },
}
bindPickerChange4: function(e) {
    console.log('picker发送选择改变，携带值为', e.detail.value)
    this.setData({
     di_index: e.detail.value
    })
  },